One of the major limitations of the use of optoacoustics (OA) for the imaging of prostate cancer is the relatively low resolution when performed in real time. The work presented in this thesis aims to address this limitation by applying frequency-based analyses, which contribute additional information on sub-resolution structures to OA images, and may prove useful for advanced detection and monitoring of prostate cancer. Optoacoustic imaging was employed to distinguish physiological differences Show moreOne of the major limitations of the use of optoacoustics (OA) for the imaging of prostate cancer is the relatively low resolution when performed in real time. The work presented in this thesis aims to address this limitation by applying frequency-based analyses, which contribute additional information on sub-resolution structures to OA images, and may prove useful for advanced detection and monitoring of prostate cancer. Optoacoustic imaging was employed to distinguish physiological differences between tissues in in vivo mouse models (transgenic adenocarcinoma of mouse prostate [TRAMP] and C57Bl6) and vascular casts of mouse renal and hepatic vasculature, and heat-induced physiological changes in ex vivo bovine liver during laser thermal therapy (LTT). Optoacoustic signal intensity and frequency spectrum analyses were performed on signals obtained from a reverse-mode OA imaging system (Seno Medical Instruments Inc., San Antonio, TX) with a 775 nm pulsed optical illumination Neoplastic prostate tissue and laser-induced tissue changes were identified based on the OA signal amplitude in combination with spectral analysis of the OA radiofrequency (RF) data. Tumours generated higher amplitude signals than those of the surrounding tissues, with contrast ratios of 33 ± 3 dB. In ex vivo bovine liver, the amplitude of the post-treatment OA signals was on average three times higher compared with pre-treatment signals. The RF spectrum analysis showed significant differences between neoplastic and normal tissues, and between pre-heated and post-heated tissues. The midband fit was 62% (5 dB) higher, the intercept 57% (4 dB) higher and the spectral slope 50% (0.4 dB/MHz) higher for neoplastic prostate tissue compared to normal tissues in the control mice. These spectral parameter values were further investigated using simple and complex phantoms and were found to relate to the size and density of the OA targets (in this case, vasculature). During LTT, the midband fit and intercept increased on average by 7 ± 1 dB and 9 ± 1 dB, respectively, and the slope decreased on average by 0.3 ± 0.1 dB. Unlike the amplitude of the OA signal, the spectral parameters were not significantly affected by the temperature of the target during LTT. The spectral parameters, thus, may have been affected primarily by tissue state (i.e. native or coagulated). Thus, this may provide a means of monitoring LTT directly using OA imaging, rather than through monitoring temperature which is often used as a surrogate of damage. The results of this study demonstrate that OA imaging provides high-contrast imaging of a murine model of prostate cancer in vivo, and real-time monitoring of LTT ex vivo. Analysis of OA frequency parameters may offer information on sub-resolution vascular structures in the neoplastic tissue. Optoacoustic frequency analysis may also offer a more direct measure of tissue thermal damage compared to temperature-based methods. Such OA frequency analysis, in combination with OA thermometry, may represent an improved strategy for monitoring LTT. This analysis technique may be applied to any OA signal to provide additional information on sub-resolution tissue structures. Overall, this represents a promising technique for improving prostate tumour detection and real-time treatment monitoring. Show less

In presenting this thesis in partial fulfillment of the requirements for a graduate degree from the University of Prince Edward Island, the author has agreed that the Robertson Library, University of Prince Edward Island, may make this thesis freely Show moreIn presenting this thesis in partial fulfillment of the requirements for a graduate degree from the University of Prince Edward Island, the author has agreed that the Robertson Library, University of Prince Edward Island, may make this thesis freely available for inspection and gives permission to add an electronic version of the thesis to the Digital Repository at the University of Prince Edward Island. Moreover the author further agrees that permission for extensive copying of this thesis for scholarly purposes may be granted by the professor or professors who supervised the author's thesis work, or, in their absence, by the Chair of the Department or the Dean of the Faculty in which the author's thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for financial gain shall not be allowed without the author's written permission. It is also understood that due recognition shall be given to the author and to the University of Prince Edward Island in any scholarly use which may be made of any material in the author's thesis. Show less
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